The answer for you depends on whether you have a regular need for data beyond flying.
If you don't, Wifi with a Stratus (assuming of course you plan to use ForeFlight) will meet your needs. If you do have a regular data need when wifi isn't available (people who think they will use it for flying generally expand their use, then you need at least data capability (a 3/4G iPad) whether or not you use a all-the-time or only-when-needed data plan.
For context, I am on my second iPad and have been using iPad+FF for 3-4 years now. It's always been wifi only and I haven't really missed data plan capability. I keep thinking my next one will have data capability, but the more time that goes by, it seems the less I need it. Other's experience is completely different.